Electro-thermal breakdown measurement of 500 kV cross-linked polyethylene submarine cable insulation material and its lifetime model analysis

The first 500 kV AC cross-linked polyethylene (XLPE) cable in the world has been installed in China in 2019. The insulation performance of insulation material under the electro-thermal stress is the basis for its service life. At here, the AC breakdown voltage values and the breakdown time of the 500 kV AC XLPE submarine cable insulation material under the electro-thermal step stress was analyzed. The lifetime prediction accuracy of a new proposed model was compared to the classic FALLOU, SIMONI/RAMU and CRINE lifetime model. Results show that the AC breakdown strength and lifetime of the XLPE samples increase slowly at low temperatures (40–65°C) and decrease rapidly at high temperatures (65–85°C). The lifetime prediction error of the classic FALLOU, SIMONI/RAMU and CRINE models present that their fit goodness cannot meet the accuracy requirement. The new lifetime model using stepwise regression method could optimize the combination of variables, which considers the coupling effect of electrical and thermal stress. The evaluation error of the new proposed model is better than the FALLOU, SIMONI/RAMU and CRINE model, which is suitable for analyzing the lifetime of the AC 500 kV XLPE submarine cable insulation material.